The present invention relates to a vehicle safety apparatus for restraining an occupant of a vehicle during a collision, and more particularly, to such an apparatus having an inflatable confinement which aspirates during inflation.
Vehicle safety devices for protecting the occupant of a vehicle by restraining his forward motion, relative to the vehicle, during a collision have become well known. Such systems include a confinement which is inflated by a flow of fluid from a reservoir to expand the confinement in time to cushion the forward movement of the occupant, absorbing his kinetic energy, and thereby preventing injury. Various problems have arisen in the development of such systems, however. The desired expansion of the confinement requires a relatively large amount of fluid, which in turn requires a fairly large, heavy fluid reservoir. In addition, if the inflator system employs pyrotechnics, i.e., the ignition or burning of a propellant fuel to facilitate the expansion of the inflation gas, there is the added problem of the heat of the inflation gas and the possible presence of toxic fumes.
It is also necessary to be able to quickly deflate the confinement, either when the confinement may engage an obstruction, such as an occupant in an unusual seating position, or immediately after the collision when it may be desirable for the occupant to exit the vehicle quickly. In the conventional inflatable restraint systems, various devices have been employed to deflate the confinement. Typical of these are the blow-out patches illustrated in U.S. Pat. No. 3,560,018. In operation, when the confinement is deployed and the pressure within the confinement exceeds a predetermined value, the patch is blown loose from the confinement, exposing an aperture therein through which the inflation gas may be exhausted. Such exhaust means are useful, but merely add to the manufacturing expense of the system and are thus undesirable.
An additional requirement which has been imposed both by the trend toward smaller cars and the desire to be able to locate the devices on the steering wheel, is an increase in the speed of inflation. Inflation of the confinement may be restricted in smaller cars because as the confinement expands, the volume of air in the passenger compartment must be either compressed or forced from the compartment.
The above and other problems encountered in the vehicle safety art have been partially solved by the development of the aspirated vehicle occupant restraint system, by which it is meant that air from outside the system is drawn into the confinement during the expansion thereof. Aspirated systems of the type illustrated in U.S. Pat. No. 3,632,133 utilize an arrangement of concentric nozzles, through one of which a stream of the inflation gas is passed into the confinement, and through the other, a larger volume of air is drawn into the confinement from outside the system, such as from under the dashboard, thus maintaining the atmospheric pressure within the passenger compartment during expansion of the confinement. In such prior art aspirated systems, the interior of the confinement is in permanent, open communication with the atmosphere outside the system and there is no possibility of control over the amount or rate of aspiration. Nor is it feasible, with a concentric-nozzle aspiration system, to utilize an elongated diffuser to distribute the inflation gas uniformly across the entire width of the confinement. Another problem which has arisen in the use of both the aspirated and conventional air bag systems is the possibility of injury to a passenger, in certain circumstances, for example, a child standing in front of the seat adjacent the dashboard. Such injury may result when the child is too close to the confinement as it begins to deploy. Therefore, it has been desirable to provide adequate exhaust or "blow-off" means for such situations.